1. Related Applications
U.S. patent application Ser. Nos. 13/563,627, 13/239,158, 13/108,933, 11/733,991, 10/975,590, and U.S. Provisional Patent Application Ser. No. 60/555,150 are each hereby incorporated by reference.
2. Background Art
Excessive interstitial fluid accumulation, referred to as edema, may arise from a variety of illnesses and conditions, including venous valvular insufficiency, postphlebotic syndrome, and lymphedema. Control of this edema by reduction of interstitial fluids is important to increase PO2 delivery to tissues, relieve pain from swelling, and decrease risk of infection. Decreasing drainage of fluid from sores, skin breaks, and/or ulcerations promotes wound closure, and prevents wound breakdown. Compression to an extremity decreases vein diameter and increases flow velocity, which decreases risk of blood clot formation.
Thus, it is desirable to have a customizable or off-the-shelf compressive device that can be readily available for application to a body part to prevent excessive fluid accumulation resulting from a variety of diseases and maladies.
The pathophysiology of venous ulceration is due to hypertension of the venous capillary system. In some cases, this is due to reflux from the venous valvular system, which occurs in older adults. Risk factors include tall height, obesity, inactivity, atherosclerosis, and history of previous deep venous blood clot.
One of the first attempts in treating venous ulceration was made by Paul Gerson Unna, a German pathologist. Dr. Unna invented a zinc paste boot to apply to the leg. This boot provided non-elastic compression to the leg, which augmented the calf-muscle pump to reduce venous hypertension. The Unna boot is still one of the leading methods of treating venous ulcerations today, although the technology has several drawbacks. First, the boot is inflexible. It provides no baseline compression. If applied to an edematous leg, the boot then reduces the edema by augmenting the calf muscle pump, and the limb girth improves. As edema reduces, however, the boot becomes loose on the leg and less effective as the edema reduces. It also loosens the dressing over the ulceration, and may lead to increased drainage and maceration of the periwound skin between the ulcer and the boot. Thus, ideally the boot would be able to conform to different size limbs as the edema reduces, maintaining therapeutic compression levels.
Attempts have been made to replace the zinc paste boot with a non-elastic leg binder. These garments are sold under the LegAssist® (Compression Design LLC, Zeeland, Mich.) and Circaid® (Circaid Medical Products Inc., San Diego, Calif.) brands, and use non-elastic bands which interlock around the limb. These garments have adjustable non-elastic bands which use hook and loop material to interconnect the bands. This type of garment has several drawbacks. Many people consider them difficult to don or remove. If the garment is applied on the leg, it does not conform to the limb shape for irregularly shaped limbs as the bands are inelastic. Furthermore, because the bands are inelastic, after the garment is donned the garment becomes loose as the edema reduces, and the garment tends to become loose and fall down. Furthermore, because the bands are inelastic, there is no simple, reliable system for a patient to tell how tight the bands are applied. Attempts to design a garment with elastic bands is also not simple. First, there is the risk the garment will be applied with too much compression and cut off circulation to the limb. Secondly, it is more important for an elastic system to have a simple reliable way to measure the pressure the band applies so dangerous compression levels are not applied.
Another attempt to replace the zinc paste boot is the short-stretch wrap. Sold under the LoPress® (Hartmann Conco Inc., Rock Hill, S.C.) name and the Comprilan® (Jobst, Charlotte, N.C.) brands, these wraps have short-stretch elasticity with low resting compression. These wraps are designed to be applied at maximal stretch. These wraps are particularly useful for lymphedema, although they also work well for venous insufficiency and other types of edema as well. In the case of lymphedema, we find that the active compression level augments the lymphangion micropump in the lymphatic system to augment lymphatic flow. The short-stretch wrap is applied at maximal stretch, so it does a good job augmenting the calf muscle pump to improve venous return. For severe venous ulcerations, they sometimes need higher levels of resting compression.
Traditional compression stockings can provide different ranges of compression that can augment calf muscle pump action. Because the stockings have to fit a range of limb girth, actual compression varies with the range. Also, fluctuations in edema within a single patient and diurnal variations during the course of the day also affect limb girth. This can make the stockings difficult, if not impossible, to don and doff. While compression stockings augment calf muscle function, they are still elastic and therefore the augmentation of the calf muscle pump is not as great as it could be. Patients often purchase weak compression range stockings because they are easier to don, only to find that the limb swells and then the patient cannot don them at all. Also, since compression stockings are made in a circular weave to fit a limited range of limb girth, they loosen as limb edema reduces. Thus, many compression experts recommend using other compression modalities to reduce edema, and then use compression stockings to prevent edema recurrence.
Thus, it would be beneficial to provide a garment that had the ability to maximally augment venous return with calf muscle activation, which also provided active compression to augment the lymphangion micropump system. Furthermore, because edema fluctuates diurnally, it would be beneficial to provide a garment that is adjustable to limb girth so that it is always applied with uniform compression. In addition, it is beneficial to provide active compression so that the garment would not loosen and slip down if limb girth decreases, and the garment would be form fitting since it had some stretch to fit around abnormally shaped limbs. An additional optimal design would be that the user could easily don the garment and get consistent levels of compression with the garment application.